Multicystic Dysplastic Kidney (MCDK) Imaging Spectrum

MCDK is the second most common neonatal abdominal mass. On ultrasound, it appears as numerous non-communicating cysts of varying sizes.

• MCDK vs UPJ obstruction: the largest cyst is never central.

• The tissue between cysts is typically echogenic, representing dysplastic, non-functional parenchyma.

• Check the contralateral kidney: 20% have anomalies (e.g., VUR, UPJO).

• Nuclear Medicine shows a complete lack of function on the affected side.

• Prognosis: Unilateral cases usually involute and are managed nonoperatively; bilateral MCDK is fatal due to pulmonary hypoplasia.

• Common for the kidney to become sonographically invisible by early childhood, leading to a "solitary" kidney appearance later in life.